Browsing by Author "Ozgener, L"

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    Energetic performance analysis of a solar photovoltaic cell (PV) assisted closed loop earth-to-air heat exchanger for solar greenhouse cooling: An experimental study for low energy architecture in Aegean Region
    Ylidiz, A; Ozgener, O; Ozgener, L
    An experimental system was developed and tested in order to investigate the energetic performance of a solar photovoltaic system (PV) assisted earth-to-air heat exchanger (underground air tunnel) that is used for greenhouse cooling at the Solar Energy Institute, Ege University, Izmir, Turkey. Average value of temperature differences between inlet and outlet of earth-to-air heat exchanger (EAHE) was observed 8.29 degrees C at experimental measurements. The average heat discharge rate (cooling load) was realized as 5.02 kW by using 0.7 kW fan. System was operated about 11 h/day. As a result, total electricity energy consumption of the system was measured to be 8.10 kWh and 34.55% of this energy demand was provided from photovoltaic cells. Furthermore, 65.45% of the electricity energy demand was provided from grid connection. Results are discussed and interpreted in the paper for various performance metrics. (C) 2012 Elsevier Ltd. All rights reserved.
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    Prediction of soil temperatures for shallow geothermal applications in Turkey
    Yener, D; Ozgener, O; Ozgener, L
    In this study, soil temperatures at different depths in Turkey's different regions were investigated theoretically. Soil temperature data are critical for different research interests such as ecology, biology, technique processes, forestry, agriculture, energy, food sector, ground heat exchanger applications, thermal energy storage applications, and so forth. This investigation gives information related to the prediction of soil temperature's dependence with depth and time especially for shallow geothermal applications. Soil temperature values depend on a great deal of varied parameters such as thermal conductivity, short term climatic conditions and moisture content. The main issue is that despite these temperatures are extremely important values, they can not be obtained in a short time. Due to this reason, we study a mathematical model related to the prediction of soil temperature. Within this context, 81 cities and their approximately 300.000 data, both, monthly air and soil temperatures between 1960 and 2015 were studied and finally seven regions in Turkey were investigated and final average soil temperature values were achieved. Measured data taken from the Izmir State Meteorological Station, and predicted soil temperatures at depths of 5 cm, 10 cm, 20 cm, 50 cm, and 100 cm were analyzed for each region in Turkey according to data obtained fifty years ago. Finally, at depths of 5 cm, 10 cm, 20 cm, 50 cm and 100 cm, the maximum average percentage errors in Turkey were 16%, 14.8%, 13.5%, 14.4%, 13.9% respectively. In conclusion, we evaluate the relationship between ambient air temperatures and soil temperatures in terms of depths from 5 to 3000 cm.
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    Monitoring of energy exergy efficiencies and exergoeconomic parameters of geothermal district heating systems (GDHSs)
    Ozgener, L; Ozgener, O
    In this work, the monitoring energy and exergy efficiency results of the last heating seasons of operation of the geothermal district heating systems (GDHSs) and their technical availability analysis and monitoring exergoeconomic parameters are presented. The case studies cover the actual system data taken from the systems in Afyon and Salihli GDHSs, Turkey. General energy, exergy, technical availability, and exergoeconomic analysis of the GDHSs are introduced. Furthermore, the average technical availability, real availability, capacity factor and energy and exergy efficiencies value of GDHSs have been analyzed. (C) 2008 Elsevier Ltd. All rights reserved.
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    Monitoring of energetic and exergetic performance analysis of Salihli Geothermal District Heating System
    Ozgener, L; Ozgener, O
    This study deals with a monitoring and assessment of energetic and exergetic analysis of Salihli Geothermal District Heating System (SGDHS) in Manisa, Turkey. In the analysis, actual system yearly average data of latest heating season are used to assess the district heating system exergetic performance. New exergetic model is improved and compared with old exergetic model results throughout the SGDHS. The new exergy losses occur particularly due to the fluid flow, taking place in the reinjection of thermal water (e.g., geothermal fluid), pumps, and the heat exchanger, as well as the natural direct discharge of the system.
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    Monitoring of Thermoeconomic Analysis of Salihli Geothermal District Heating System (SGDHS)
    Ozgener, L; Ozgener, O
    The paper describes briefly thermoeconomic analysis of Salihli Geothermal District Heating System (SGDHS) in Turkey. The case study covers the actual system data taken from the SGDHS, Turkey. General thermoeconomic analysis of the SGDHS is introduced. Then this analysis applied to SGDHS using actual thermodynamic data for its performance evaluations in terms of thermoeconomic parameter is presented.
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    Energetic performance test of an underground air tunnel system for greenhouse heating
    Ozgener, L; Ozgener, O
    The main objective of the present study is to investigate the performance characteristics of an underground air tunnel (UAT) for greenhouse heating with a 47 m horizontal, 56 cm nominal diameter U-bend buried galvanized ground heat exchanger. This system was installed in the Solar Energy Institute, Ege University, Izmir, Turkey. Based upon the measurements made in the heating mode, the average heat extraction rate to the soil is found to be 3.77 kW, or 80.21 W/m of tunnel length, while the required tunnel length in meters per kW of heating capacity is obtained as 12.46. The entering air temperature to the tunnel ranges from 14.3 to 21.5 degrees C, with an average value of 15.5 degrees C. When the system operates, the greenhouse air is at a minimum day temperature of 13.1 degrees C with a relative humidity of 32%. The maximum heating coefficient of performance of the UAT system is about 6.42, while its minimum value is about 0.98 at the end of a cloudy and cold day and fluctuates between these values at other times. The daily average maximum COP values for the system are also obtained to be 6.42. The total average COP in the heating season is found to be 5.16. (C) 2010 Elsevier Ltd. All rights reserved.
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    Modeling of driveway as a solar collector for improving efficiency of solar assisted geothermal heat pump system: a case study
    Ozgener, O; Ozgener, L
    It is well known that rooftop solar thermal panels increase both power rates of circulation pumps and initial investment cost of solar assisted ground source (geothermal) systems. To avoid both of them it means that the unnecessary energy consumption rates of circulation pump(s) and their initial capital cost, rather than installing rooftop solar thermal panels, driveways can be used as solar collectors for improving efficiency of geothermal heat pump systems (GSHP) and declining initial capital cost of SAGSHPs. Mainly this idea was first put in the middle by Jefferson W. Tester. In this paper, we will examine modeling of driveway as solar thermal panel to enhance efficiency of solar assisted geothermal heat pump system (SAGSHP) depends on its different operating types; yet we will give only a case that is investigated theoretically for solar assisted geothermal heat pump systems. (C) 2015 Elsevier Ltd. All rights reserved.
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    Parametric study of the effect of reference state on energy and exergy efficiencies of a small industrial pasta drying process
    Ozgener, L; Ozgener, O
    The paper describes a performance evaluation of the industrial pasta process system in Gaziantep, based in Turkey, on energy and exergy analyses. The case study covers the actual system data taken from the system. General energy and exergy analysis of the system are introduced. This analysis, applied to the system using actual thermodynamic data for its performance evaluation in terms of energy and exergy efficiencies, is presented. In addition a parametric study of the effect of varying reference state properties on the energy and exergy efficiencies of the system has been conducted to find optimum performance and operating conditions, and is explained.
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    Exergetic assessment of EAHEs for building heating in Turkey: A greenhouse case study
    Ozgener, O; Ozgener, L
    The present study undertakes an exergy analysis of earth to air heat exchanger (EAHE) and applies to a local one in Turkey. Namely, the exergy performance of an EAHE has been evaluated in a demonstration in Solar Energy Institute of Ege University, Izmir, Turkey. Exergetic efficiencies of the system components are determined as an attempt to assess their individual performances. The daily maximum heating coefficient of performance (COP) value for the system is obtained to be 6.18. The total average COP in the experimental period is found to be 4.74. (C) 2010 Elsevier Ltd. All rights reserved.
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    Determining the optimal design of a closed loop earth to air heat exchanger for greenhouse heating by using exergoeconomics
    Ozgener, O; Ozgener, L
    This investigation deals with an exergoeconomic evaluation of the earth to air heat exchanger (EAHE) application for determining the optimal design greenhouse heating in Izmir, Turkey. The exergy destructions in the system are quantified and illustrated using tables for a reference temperature of 6 degrees C. The results indicate that the exergy destructions in the system occur primarily as a result of blower losses and heat exchanger losses. These average losses account for 85% and 4.5%. respectively. Both COP and exergy efficiency of the overall system was investigated to analyze and improve the systems performance. The average COP and exergetic efficiency were determined to be 10.51 and 89.25%, respectively. The results may provide useful insights into the relations between thermodynamics and economics for the EAHE heating systems. (C) 2010 Elsevier B.V. All rights reserved.
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    Thermomechanical exergy and thermoeconomic analysis of geothermal district heating systems
    Ozgener, L; Ozgener, O
    The current paper presents the thermomechanical exergy and thermoeconomic analysis of geothermal district heating systems (GDHSs) in Turkey. The case studies cover the actual system data taken from the systems in Afyon, Gonen, and Salihli GDHSs, Turkey. General energy and exergy analysis of the GDHSs are introduced. Then the analysis applied to these GDHSs using actual thermodynamic data for their performance evaluations in terms of energy and exergy efficiencies are presented. Besides, thermoeconomic evaluations of GDHSs are given in tables.
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    Exergoeconomic analysis of an underground air tunnel system for greenhouse cooling system
    Ozgener, O; Ozgener, L
    This paper investigates some exergoeconomic parameters for an underground air tunnel system based upon some operating conditions. The ratio of exergy loss rate to capital cost (R(ex)) changes between 0.052 and 0.552. The total exergy losses values are obtained to be from 0.26 kW to 2.50 kW for the system. The daily average maximum cooling coefficient of performances (COP) values for the system are also obtained to be 11.96 for experimental period, while the total average COP is found to be 5.89. The overall exergy efficiency value for the system on a product/fuel basis is found to be 56.9%. (C) 2010 Elsevier Ltd and IIR. All rights reserved.
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    Exergy Analysis of Drying Process: An Experimental Study in Solar Greenhouse
    Ozgener, L; Ozgener, O
    This article examines the exergy variation during drying in solar greenhouses. Exergy efficiencies were derived as functions of drying time and temperature of the drying air. An illustrative example is considered to verify Dincer and Sahin's model and to show the applicability of the model to actual drying processes at different drying air temperatures. This work is intended not only to demonstrate the usefulness of exergy analysis in thermodynamic assessments of drying processes but to provide insights into their performances and efficiencies. In this study, the drying performance of the passively heated solar greenhouse has been investigated. Experimental results under the meteorological conditions of Izmir, Turkey (latitude 38.24 N, longitude 27.50 E), are presented.
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    PERFORMANCE ANALYSIS OF GEOTHERMAL DISTRICT HEATING AND GEOTHERMAL HEAT PUMP APPLICATIONS IN BUILDINGS
    Ozgener, L; Ozgener, O
    This study describes Geothermal District Heating Systems (GDHSs) and Geothermal Heat Pumps (GHPs) and their energetic and exergetic performance analysis. The case studies cover the actual system data taken from the systems, Turkey. General energy and exergy efficiencies of the GDHSs and GHP are introduced. Then this analysis applied to selected GDHS and GHP system using actual thermodynamic data for theirs recent performance evaluations in terms of energy and exergy efficiencies.
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    An experimental study of the exergetic performance of an underground air tunnel system for greenhouse cooling
    Ozgener, L; Ozgener, O
    The present study highlights the exergetic performance characteristics of an underground air tunnel for greenhouse cooling with a 47 m horizontal, 56 cm nominal diameter U-bend buried galvanized ground heat exchanger. This system was designed and installed in the Solar Energy Institute, Ege University, Izmir, Turkey. Underground air tunnel systems, also known as earth-to-air heat exchangers, are recognized to be outstanding heating. cooling and air heating systems. On the other hand, they have not been used yet in the Turkish market. Greenhouses also have important economical potential in Turkey's agricultural sector. Greenhouses should be cooled during the summer or hot days. In order to establish optimum growth conditions in greenhouses, renewable energy sources should be utilized as much as possible. It is expected that effective use of underground air tunnels with a suitable technology in the modern greenhouses will play a leading role in Turkey in the foreseeable future. The exergy transports between the components and the destructions in each of the components of the system are determined for the average measured parameters obtained from the experimental results. Exergetic efficiencies of the system components are determined in an attempt to assess their individual performances and the potential for improvements is also presented. The daily maximum cooling coefficient of performances (COP) values for the system are also obtained to be 15.8. The total average COP in the experimental period is found to be 10.09. The system COP was calculated based on the amount of cooling produced by the air tunnel and the amount of power required to move the air through the tunnel, while the exergetic efficiency of the air tunnel is found to be in a range among 57.8-63.2%. The overall exergy efficiency value for the system on a product/fuel basis is found to be 60.7%. (C) 2010 Elsevier Ltd. All rights reserved.
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    Exergy analysis of industrial pasta drying process
    Ozgener, L; Ozgener, O
    In this study we present an energy and exergy modelling of industrial final macaroni (pasta) drying process for its system analysis, performance evaluation and optimization. Using actual system data, a performance assessment of the industrial macaroni drying process through energy and exergy efficiencies and system exergy destructions is conducted. The heat losses to the surroundings and exergy destructions in the overall system are quantified and illustrated using energy and exergy flow diagrams. The total energy rate input to system is 316.25 kW. The evaporation rate is 72 kg h(-1) (0.02 kg s(-1)) and energy consumption rate is found as 4.38 kW for 1 kg water evaporation from product. Humidity product rate is 792 kg h(-1) (0.22 kg s(-1)) and energy consumption rate is found about 0.4 kW for 1 kg short cut pasta product. The energy efficiencies of the pasta drying process and the overall system are found to be as 7.55-77.09% and 68.63%. The exergy efficiency of pasta drying process is obtained to be as 72.98-82.15%. For the actual system that is presented the system exergy efficiency vary between 41.90 and 70.94%. Copyright (c) 2006 John Wiley & Sons, Ltd.
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    Exergoeconomic assessment of a wind turbine power plant (WTTP): Cesme, Izmir, example
    Baskut, O; Ozgener, L
    This present paper deals with exergoeconomic results of the Wind Turbine Power Plants (WTPPs) for the first time to our knowledge. Ratio of exergy loss rate to capital cost-exergy efficiency graph and correlation are presented. Monthly exergoeconomic results are also presented for the three turbines. Ratio of exergy loss rate to capital cost and ratio of energy loss rate to capital cost depending on the wind speed are studied. And also as meteorological variables temperature (density of air) and humidity effect on ratio of exergy loss rate to capital cost are discussed and the results are given by the table and graphs clearly. The paper describes an exergoeconomic evaluation of wind turbine power plant. The analysis of the field data demonstrates the proposed system is a viable option for wind turbine power plant (WTTP) installations. (C) 2012 Elsevier Ltd. All rights reserved.
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    ANALYSIS OF SOME EXERGOECONOMIC PARAMETERS OF A SMALL WIND TURBINE SYSTEM
    Ozgener, O; Ozgener, L; Dincer, I
    This paper investigates some exergoeconomic parameters (energy and exergy loss ratios) for a 1.5 kW wind turbine system, linking capital costs and thermodynamic losses, based on some operating conditions. The results show that while the ratio of energy loss rate to capital cost (R-en) changes between 0.007 and 0.813 at different wind speeds, the ratio of exergy loss rate to capital cost (R-ex) changes between 0.006 and 0.411. In addition, the maximum Ren and Rex values are obtained at a wind speed of 12 m/s. Furthermore, a parametric study is undertaken to investigate how varying wind speed will affect the exergoeconomic parameters of the wind turbine system and to develop a correlation between the ratio of thermodynamic loss rate to capital cost and wind speed for practical applications of wind energy systems.
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    Three Cooling Seasons Monitoring of Exergetic Performance Analysis of an EAHE Assisted Solar Greenhouse Building
    Ozgener, O; Ozgener, L
    The present manuscript experimentally investigated the exergetic performance (efficiency) of a closed loop earth to air heat exchanger (underground air tunnel) in the cooling mode. The experimental system was commissioned in June 2009 and experimental data collecting have been conducted since then. The data, consisting of hourly thermodynamics records a year cooling period, 2009-2011, were measured in the Solar Energy Institute of the Bornova Campus at Ege University. At the present time, the database contains more than 40,000 records of measurements. Exergetic efficiencies value of the system and system components have been analyzed. Furthermore, a long term exergetic modeling of a closed loop earth-to-air heat exchanger solar greenhouse cooling system for system analysis and performance assessment is presented. Exergetic efficiency of the system and its compenents at various reference states are also determined.
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    Exergoeconomic analysis of geothermal district heating systems: A case study
    Ozgener, L; Hepbasli, A; Dincer, I; Rosen, MA
    An exergoeconomic study of geothermal district heating systems through mass, energy, exergy and cost accounting analyses is reported and a case study is presented for the Salihli geothermal district heating system (SGDHS) in Turkey to illustrate the present method. The relations between capital costs and thermodynamic losses for the system components are also investigated. Thermodynamic loss rate-to-capital cost ratios are used to show that, for the devices and the overall system, a systematic correlation appears to exist between capital cost and exergy loss (total or internal), but not between capital cost and energy loss or external exergy loss. Furthermore, a parametric study is conducted to determine how the ratio of thermodynamic loss rate to capital cost changes with reference temperature and to develop a correlation that can be used for practical analyses. The correlations may imply that devices in successful district heating systems such as the SGDHS are configured so as to achieve an overall optimal design, by appropriately balancing the thermodynamic (exergy-based) and economic (cost) characteristics of the overall systems and their devices. (c) 2006 Elsevier Ltd. All rights reserved.